The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A vehicle may include an internal combustion engine (ICE) that generates drive torque. The ICE combusts an air/fuel mixture within cylinders to drive pistons that produce the drive torque. The air/fuel mixture is regulated via intake and exhaust valves. The intake valves are selectively opened to draw air into the cylinders. The air is mixed with fuel to form the air/fuel mixture. The exhaust valves are selectively opened to allow exhaust gas to exit from the cylinders after combustion of the air/fuel mixture.
The engine may include one or more camshafts that regulate opening and closing times of the intake and exhaust valves. The camshafts include cam lobes that each has a profile that is associated with a valve lift schedule. The valve lift schedule includes an amount of time a valve is open (i.e. duration) and a magnitude or degree to which the valve opens (i.e. lift).
Variable valve actuation (VVA) technology improves fuel economy, engine efficiency, and/or performance by modifying a valve lift event, timing, and duration as a function of engine operating conditions. Two-step VVA systems include variable valve assemblies such as hydraulically controlled switchable roller finger followers (SRFFs). SRFFs enable two discrete valve states (e.g. a low-lift state and a high-lift state) for the intake and/or exhaust valves. Example SRFFs are provided and described in U.S. application Ser. No. 12/062,920, filed on Apr. 4, 2008, and U.S. application Ser. No. 11/943,884, filed on Nov. 21, 2007.
An engine control module (ECM) may transition a SRFF mechanism from a low-lift state to a high-lift state and vice versa based on demanded engine speed and load. For example, an ICE operating at an elevated engine speed, such as 3,000 revolutions per minute (RPM), typically requires the SRFF mechanism to operate in a high-lift state to avoid potential hardware damage to the ICE.
The SRFF mechanism may be actuated by an oil control valve (OCV) that controls one or more SRFFs. The OCV may be used to control a flow of engine oil to control the SRFFs associated with the OCV. Improper operation of the OCV may cause improper operation of and/or damage to an SRFF. An improperly operating SRFF may cause an intake and/or exhaust valve to be stuck in one of the low-lift or high-lift states.